Update updating-docker docs

Author: keithduncan

docs/updating-docker.md

@@ -1,30 +1,33 @@
 # Updating Docker
 
+See https://github.com/buildkite/elastic-ci-stack-for-aws/pull/954 for an
+example of updating Docker for Linux and Windows.
+
 ## Linux
 
 Packer installs Docker, docker-compose, and `docker buildx` using the [`packer/linux/scripts/install-docker.sh`](packer/linux/scripts/install-docker.sh)
-script.
+script. Update the `DOCKER_VERSION` variable in this file to change which
+version of Docker is installed. Update the `DOCKER_COMPOSE_VERSION` variable to
+change which version of docker-compose is installed. Update the
+`DOCKER_BUILDX_VERSION`variable to change which version of `docker buildx` is installed.
 
 Binary releases are downloaded directly from Docker and GitHub.
 
-Update the `DOCKER_VERSION` variable to change which version of Docker is
-installed. Update the `DOCKER_COMPOSE_VERSION` variable to change which version
-of docker-compose is installed. Update the `DOCKER_BUILDX_VERSION` variable to
-change which version of `docker buildx` is installed.
-
 ## Windows
 
 Packer installs Docker, and `docker-compose` using the [`packer/windows/scripts/install-docker.ps1`](packer/windows/scripts/install-docker.ps1)
 script.
 
 [MicrosoftDockerProvider](https://github.com/OneGet/MicrosoftDockerProvider)
 is used to source Docker packages. The list of available packages that it 
-installs can be found at https://dockermsft.azureedge.net/dockercontainer/DockerMsftIndex.json
+installs can be found at https://dockermsft.azureedge.net/dockercontainer/DockerMsftIndex.json.
 
-Update the `docker_version` variable to one of the available package versions
-to change which version of Docker is installed. 
+Update the `docker_version` variable in `install-docker.ps1` to one of the
+available package versions to change which version of Docker is installed.
 
-The `choco` package manager is used to install `docker-compose`.
+The `choco` package manager is used to install `docker-compose`. See the
+[chocolatey package manager version history](https://community.chocolatey.org/packages/docker-compose#versionhistory)
+for a list of available versions.
 
-Update the `docker_compose_version` variable to change which version of
-`docker-compose` is installed.
+Update the `docker_compose_version` variable in `install-docker.ps1` to change
+which version of `docker-compose` is installed.